1. Field of the Invention
This invention relates generally to the field of valves for water systems, and more specifically, to an improved gate valve for a hydraulic system.
2. Related Art
There is much interest expressed by the hydraulics industries, hydraulic equipment industries, and other parties in improved valves for regulating flow in fluid systems. By way of example, both the U.S. Government and private industry are interested in improved valves as a control component for existing dams, future dams, outer works, siphons, or other suitable pressurized water delivery systems.
The utility of improved valves is not limited to the hydraulic industry. It may additionally have significant application potential in many other industries. These other applications include use in nozzles for hydraulic cleaning equipment, in nozzles for coating or spray applications, in gas thrusters for the aerospace industry, in water thrusters for the marine industry, in atomizers for the automotive and combustion industries, and as gas expansion valves for the HVAC for the cryogenic industries.
In one common application, heavy duty control valve apparatus are incorporated at the outlets of large hydraulic conduits, particularly in river and canal outlet works, bypass lines and energy dissipaters for either submerged or free release. The valves variably restrict water discharge through the outlets, and are preferably controllable between fully open and fully closed positions.
Three of the most common types of valve configurations for hydraulic conduits are ensign valves, hollow get-flow gate valves, and valves with clamshell gates.
Disadvantages of ensign valves include the location of these valves on an up-stream dam face. This makes the valves difficult to access for maintenance purposes. In addition, ensign valves have less flow capacity than other valve arrangements,. Finally, the use of these valves may lead to cavitation damage in a downstream conduit, i.e. damage due to low hydraulic pressure pockets, just downstream of the valve surface at the water-conduit interchange.
Hollow jet-flow got gates have disadvantages as well. For example, these gates have a lowered flow capacity compared with other valve arrangements, and have the potential to cause cavitation damage to the valve itself.
Clamshell gates currently represent the best in available technology for a number of hydraulic applications. This is particularly true of dam rehabilitation projects. However, there are difficulties with the fabrication and sealing of clamshell gates and the cost of fabrication of clamshell gates for achieving adequate seal performance is high. Further, the actuators of clamshell gates are complicated.
There is specific interest in the field with respect to improving the sealing capabilities of gated valves while enhancing the ease of construction. When the gates of a dual gate valve system are in a closed position, it is important that the seal between the gates be complete so as to prevent leakage between the gates. It is also important that leakage at the edge of the conduit be prevented. These goals can be accomplished with the use of seals. However, it is important that valves with such seals be designed so as to minimize seal wear and decrease construction costs.
Attempts have been made within the art to improve the design of fluid valves. Prior art of interest in the field of fluid valves includes U.S. Pat. No. 6,009,899 (Polutnik); U.S. Pat. No. 5,692,470 (Sattler et al.); U.S. Pat. No. 5,160,119 (Lemire et al.); U.S. Pat. No. 4,844,292 (Lonardi et al.); and U.S. Pat. No. 3,998,426 (Isbester). The Polutnik patent and the Lemire patent disclose the use of dual leaf slide gates. The Lonardi et al and Sattler et al patents disclose gates having leaves movable by at least one pivoting arm. The Lonardi patent discloses a dual leaf gate-valve assembly, wherein the leaves are moved by pivoting arms. The Sattler patent is a single leaf gate-valve assembly, wherein the leaf is moved by a pivoting arm. The Isbester patent is a dual leaf clamshell design, wherein the respective leaves are rotated into a sealing position.
In accordance with the invention, a gate valve unit is provided for controlling the flow of a fluid through a conduit The unit comprises: a valve body having an outlet end and an inlet end and including, at the inlet end thereof, a conduit connector member for connecting the valve body to a fluid conduit; a valve face block having a first end and a second end, the second end being connected to the valve body, and the first end of the face block including first and second surfaces sloped backwardly from a central transverse separating edge located therebetween, the face block further including first and second sets of gate guides, each set of gate guides being located on opposite sides of one of the surfaces; the valve body, the connector member and the face block each including a central opening therein providing a central passage for fluid flow through the unit; a first and second movable gate leaves disposed respectively on the first and second surfaces of the face block and retained thereon by the gate guides so as to be movable away from and toward the central passage to thereby open and close the central passage and to thus control fluid flow through the unit; means for controlling the movement of the first and second gate leaves so as to open and close the valve unit; at least one face seal providing a seal between the surfaces of the face block and the gate leaves; a visor seal attached to the valve body and movable between an operative position, wherein the visor seal provides sealing between the gate leaves, and an inoperable position away from the gate leaves so as to not interfere with the operation of the gate leaves; and means for controlling the movement of the visor seal.
Preferably, the valve body has a cylindrical shape, the gate leaves are of rectangular shape, and the first and second surface of the face block are shaped to support the gate leaves.
Advantageously, the means for controlling the movement of the pair of gate leaves comprises at least one linear actuator. Preferably, the at least one linear actuator comprises first and second linear actuators for controlling the first and second gate leaves, respectively. Preferably, the at least one linear actuator comprises an actuator selected from the group consisting of mechanical actuators, pneumatic actuators, and hydraulic actuators.
Advantageously, the means for controlling the movement of the visor seal comprises at least one visor seal actuator. Preferably, the visor seal actuator comprises a linear actuator.
Advantageously, the visor seal comprises a visor member pivotally connected to the valve member and a seal element disposed on an inside surface of the visor member so that, in the operative position of the visor seal, the seal element faces an area of abutment of the gate leaves in the closed location thereof.
Preferably, the valve body and the face block comprises a single integral component.
Advantageously, the at least one face seal comprises an o-ring seal.
Preferably, the first and second surfaces of the valve face block slope backwardly from the central transverse separating edge at an angle of about 60xc2x0, or slope backwardly at an angle of about 45xc2x0.
Among other advantages, the gate valve of the invention controls flow in a pressurized system, such as a pressurized pipe system, while eliminating potential cavitation damage. Further, the invention provides improved sealing performance at a reduced cost of construction.
The gate value of the invention provides high capacity flow control for outlet works, siphons, or other pressurized conduits. The gate valve can be installed at the downstream end e.g. at the downstream face of a dam, of any pressurized conduit to provide flow control over a full range of gate settings, ranging from 0-100% opened. The gate valve can also be used as an in-line flow control component. Additionally, the gate valve of the invention can be operated in a free discharge or a submerged discharge mode.